A gear pump of this kind is known from DE 90 11 156.7 U1. This known gear pump serves for pumping high viscosity hardening fluids. When pumping such fluids, it is necessary to avoid entry of the fluid into the bearings of the gear wheels. Such entry would lead to interruption of the operation of the gear pump since such fluid would harden in the bearings and result in an increased bearing resistance producing strong resistance heating which would lead to carbonization of the material pressed into the bearings, whereby the bearings would freeze and put the pump out of operation. Hence in the gear pump of DE 90 11 156.7 U1, shaft seals and an axially working return screw were provided whereby the gear wheel had a central recess in which there projected a bearing housing which on its out side had a return screw and on its inner side had a packing. The gear wheels are supported by a bearing on only one side, because with this type of bearing, the number of packings and return screws are only half of those required for a double sided bearing. This single sided bearing has, however, the disadvantage that under high pressure acting on the end of the gear wheel the shaft elastically bends in the bearing and the gear wheel is canted in the housing which makes it necessary for the gap between the end face of the bearing and the housing wall to be dimensioned sufficiently great as to permit such canting of the gear wheel. This further leads to a greater leakage flow and thereby to more compound remaining in the housing.
From U.S. Pat. No. 4,336,213 it has become known to provide bearings on both sides of the gear wheels of a gear pump. From DE 328 963 it is known to support a gear wheel on a one sided journal so that the bearing extends into a recess of the gear wheel. This bearing by means of ball bearings on a one sided journal does not have the required precision to make the gap between the end face of the gear wheel and the housing sufficiently narrow as is desired in order to have the least possible amount of the material being pumped enter this gap.